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A New Channel of Hydrogen Elimination in the 121.6-nm Photodissociation of Formic Acid Detected by a Doppler-Selected TOF Mass Spectrometry
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Michihiro HASHINOKUCHIa), b), Ryoji KOUMURAa), Dock-Chil CHEb), Hiroshi OHOYAMAa), and Toshio KASAI*a), b)
*a)Department of Chemistry, Graduate School of Science, Osaka University (Toyonaka, Osaka 560-0043, Japan) b) Institute for Molecular Science (Myodaiji, Okazaki 444-8585, Japan)
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Hydrogen-atom elimination channels in 121.6-nm photodissociation of formic acid were investigated by a Doppler-selected TOF mass spectrometry (DS-TOF-MS). This mass spectroscopic method enables us to map out three dimensional velocity distributions of photodissociated products through multiphoton ionization for the H atoms, and therefore we can determine anisotropic parameter b. The H+HCOO* channel is found to be a main branching among many H elimination channels. A new three-body channel of H+CO+OH is observed. We estimate that the H+HCOO* channel is more favor than the H+CO+OH channel by a factor of  5. Other H-elimination channels such as H+HCOO, 2H+CO2, H+HOCO, and H+CO+OH(A) are found to be small. These results show that the DS-TOF-MS method is useful to determine branching ratios and internal energy distributions of photodissociated products in excited states as well as ground states in addition to anisotropic parameter determination.
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Key words:
Doppler-selected TOF mass spectrometry, Formic Acid, Hydrogen elimination channels, Branching ratios
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